By Alex Jensen

SEOUL

 South Korea is set to take an important first step towards being able to reprocess spent nuclear fuel Wednesday, enacting an upgraded deal with its military ally the United States.

Under their previous agreement, the South was forced to rely on imported nuclear fuel without being able to recycle it -- the storage of the depleted waste prompting safety concerns in a country where a third of the electricity demand is met by 24 nuclear reactors.

Having reached a new 20-year accord with the U.S. in April, Seoul's foreign ministry announced that it would be brought into force later Wednesday during a ceremony with American Ambassador Mark Lippert.

Negotiations were highly sensitive for years because of Washington's push to denuclearize the Korean Peninsula -- focusing particularly on the North.

While North Korea has largely ignored international calls to curtail its weapon ambitions, the South could also point to the virtual nuclear power status afforded to Japan, its neighbor to the east and another U.S. ally.

South Korea will now have the opportunity to develop technology known as pyroprocessing.

The next step, according to Seoul, will be talks with the U.S. starting January to discuss further deals.

The South is looking to be able to carry out its own uranium enrichment, allowing the nation to rely less on imports and boost outbound shipments -- but also giving it the potential to expand beyond peaceful pyroprocessing towards nuclear weapon production.